The epithelial-mesenchymal transition (EMT) is a transdifferentiation program that effects critical steps of embryogenesis by interconverting epithelial cell types into cells with mesenchymal attributes. EMT programs are also activated in carcinoma cells, enabling them to acquire cellular traits associated with high-grade malignancy, including the ability to complete various steps of the metastatic cascade. In addition to mesenchymal traits, recent findings suggest that adult epithelial cells that pass through an EMT also acquire properties associated with normal tissue stem cells (SCs) and tumor-initiating cells. There is significant interest in the art in inducing or inhibiting EMT programs.